<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<body>
		<script type="text/javascript">
			var num=parseInt(prompt("输入倒正金字塔的高度",""));
			document.write("<h1>打印倒正金字塔直线</h1>");
			for(var i=num;i>1;i--){
				var w=100*i-50+"px";
				document.write("<hr width="+w+"/>")
			}
			for(var i=0;i<num;i++){			
				var h=100*i+50+'px';
				document.write("<hr width="+h+"/>")
			}
		</script>
	</body>
</html>
